MRAM Packaging with Stacked Magnetic Shields
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Solution Overview
Problem
Magnetoresistive Random Access Memory (MRAM) devices are prone to errors due to interference from external magnetic fields, which affects data programming and retention, necessitating effective shielding to maintain high performance and density.
Innovation Solution
The implementation of a stacked chip-scale packaging method using high permeability metals like nickel-iron alloys as magnetic shields, integrated into the packaging process through adhesive application and photolithography, to protect magnetically sensitive memory cells from both internal and external magnetic fields, while also utilizing stress buffer materials for thermal protection and size reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MRAM devices are used without magnetic shielding, then device complexity is reduced and manufacturing is simpler, but the devices are prone to errors due to external magnetic field interference
Solution Approach 1:
A magnetic shield layer made of high permeability material is introduced as an intermediary between the external environment and the magnetoresistive memory cells. This shield layer deflects external magnetic fields around the sensitive memory cells, preventing field interference while allowing the memory device to maintain its functional structure. The shield acts as a mediator that protects the internal magnetic domains from external perturbations.
Solution Approach 2:
The packaging structure employs composite materials combining high permeability magnetic shielding materials with standard semiconductor packaging materials. The magnetic shield layer is integrated with the packaging substrate and encapsulant to create a composite structure that provides both mechanical protection and magnetic field shielding, thereby improving reliability without excessive complexity increase.
2Quantity of substance
If stacked chip-scale packaging is implemented to increase memory density, then effective density improves, but the devices become more susceptible to internal magnetic field interference between stacked layers
Solution Approach 1:
The stacked memory structure is segmented into multiple independently shielded layers. Each magnetoresistive memory die in the stack is surrounded by its own magnetic shield layer, creating isolated magnetic environments. This segmentation prevents magnetic field coupling between adjacent stacked layers, allowing high memory density to be achieved without internal interference.
Solution Approach 2:
Magnetic shield layers are nested within the stacked package structure, with each shield layer positioned between and around the magnetoresistive memory dies. The nested arrangement of shields within the compact stacked configuration provides individual protection to each memory layer while maintaining the high-density three-dimensional architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively shields MRAM devices from external magnetic interference, enhances memory density and performance, and maintains reliability and durability, allowing for higher effective density without size increase, while being cost-effectively integrated into existing manufacturing processes.
Implementation Method 1
high permeability metals like nickel-iron alloys as magnetic shields... to protect magnetically sensitive memory cells from both internal and external magnetic fields
Data Source
AI summary
A magnetoresistive memory device 20 includes dies 24 and 38, each of which contains magnetically sensitive material 50. A method 64 of packaging the magnetoresistive memory device 20 entails coupling the die 24 to a substrate 22, forming interconnections 52 between bonding pads 32 on the die 24 to connection sites 54 spaced apart from the die 24. A magnetic shield 36 is bonded to a top surface 30 of the die 24 following formation of the interconnections 52. The die 38 is attached to the magnetic shield 36, interconnections 56 are formed between bonding pads 44 on the die 38 to connection sites 58 spaced apart from the die 38, and a magnetic shield 48 is adhered to the die 38 following formation of the interconnections 56.